The present invention relates generally to printing presses and other imaging devices and more particularly to an image-carrying cylinder.
In a web offset lithographic printing press, a printing plate for an image to be printed is inked, and the image is then transferred to a blanket, which transfers the image to a continuous web of material. The printing press typically has four printing units, each for printing one of four colors on the web. As the web passes by the blanket cylinders of the printing units, it becomes moist, which can lead to an expansion of the web. The expansion of the web in the axial direction of the printing cylinders is known as web fanout. If fanout occurs, the print or images on the web thus expand slightly as the web passes each printing unit. The second and further printing units need to be properly registered with respect to the web images or print in an axial direction of the cylinders, so that, for example, a second color is applied by the second print unit directly over an image already printed by the first printing unit.
U.S. Pat. No. 4,207,815 purports to disclose a two-plate plate cylinder. One plate fits on a large diameter portion and another plate fits on a tube rotatable and axially movable with respect to the large diameter portion. The tube is fastened to a stepped shaft. Helical gearing is provided to set the axial and circumferential register of the plates. In such a device fretting and corrosion problems may occur between the tube and the stepped shaft. Also, it may be difficult to print multiple web widths on a triple wide press using such a device since the location of the boundary between the large diameter portion and the tube depends on the web width.
U.S. Pat. No. 5,383,393 purports to disclose a multicolor lithographic rotary press comprising a plurality of printing sections arranged along a traveling line of a paper web, a plurality of register adjusting means, a paper stretching means, and a plurality of width adjusting means. Each of the printing sections further includes at least one divided plate cylinder, each divided section of which is independently moved in the axial direction and/or circumferential direction. The device of the '393 patent further discloses a register adjusting means mechanically connected to each of the divided plate cylinders in the printing sections, and includes an adjusting mechanism for actuating the divided sections in response to the control unit connected to a sensor for detecting the lines and images printed on the paper web by each of the printing sections. Problems with such a device are that the paper stretching and/or paper adjusting means, such as bustle rollers, have a limited control range and may smear the print.
Commonly-owned U.S. Ser. No. 09/627,639 entitled “Multi-Plate Plate Cylinder for a Printing Press”, which is hereby incorporated by reference herein, discloses a multi-plate plate cylinder having independently registerable shells. Commonly-owned U.S. Ser. No. 09/675,494 entitled “Web Fanout Control System”, which is hereby incorporated by reference herein, discloses a web fanout control system for a printing press having multiple images carrying by the plate cylinder. Commonly-owned U.S. Ser. No. 09/948,232 entitled “Printing Press with Multiple-Image-Carrying Cylinder”, which is hereby incorporated by reference herein, discloses a multiple-image-carrying cylinder having an axially movable ring located between a shell and a cylinder section, the ring capable of having another part of a first image when connected to the cylinder section and capable of having another part of a second image when connected to the shell. These commonly-owned applications are not necessarily prior art to the present invention.